1. Field of the Invention
The present invention relates to plasma processing systems.
2. Discussion of the Background
Oxide etch processes, such as high aspect ratio contact etching and self-align contact etching, have requirements for etch rate, side-wall profile, selectivity, etc., in order to ensure viability of the finished product. In order to achieve state-of-the-art oxide etch performance and meet the requirements for most oxide etch processes, conventional wisdom suggests that the plasma chemistry should be optimized to form specific etch reactants. For instance, most people in the semiconductor community believe in utilizing a proper balance between polymers such as carbon containing species (e.g. CF, CF2 and CF3) and other reactive species such as fluorine radical. In many cases, it is desirable to produce a carbon polymer with low fluorine content in order to form protective films over non-oxide surfaces (such as SiN or poly-Si), while still permitting oxide etch. However, a large amount of CxFy radical species can lead to a stop in etching due to the accumulation of polymers. Additionally, an excessive amount of fluorine radicals can lead to poor etch selectivity of oxide-to-silicon or SiN, since the fluorine radicals will readily etch both materials. Therefore, several etch parameters including etch selectivity (i.e. oxide-to-silicon), etch rate, side-wall profile, etc. are sensitively determined based upon the dissociation condition.
In general, capacitively coupled plasma (CCP) reactors have featured medium to high density plasmas and relatively small reaction volumes, and therefore CCP reactors have not been preempted to seek new means for dissociation control. However, with an increasing need to move towards higher plasma densities, control of the dissociation condition poses a greater demand for attention. To the contrary, inductively coupled plasma (ICP) sources, as well as others (e.g. electron cyclotron resonance (ECR)), have featured high density plasmas and relatively large reaction volumes. Such systems require immediate attention to control dissociation.
One approach used to control the dissociation condition is to present the reaction volume with a scavenging source to introduce material capable of xe2x80x9cscavengingxe2x80x9d or bonding with free fluorine radicals present in the reaction volume. For example, in an oxide etch, the scavenging source might be a silicon reactor liner, silicon upper electrode, etc., or it might be a silicon containing gas such as silane. Other surfaces in the reactor may be fabricated from quartz, and these surfaces may be used to getter carbon polymer. The efficacy of these surfaces to act as scavengers is heavily dependent on the temperature of the surface. Hence, with the correct balance of carbon polymer removal or lack of removal, and the introduction of silicon to scavenge fluorine, the etch process may be fine tuned for optimal process performance (or optimal plasma chemistry). However, the use of scavenging and gettering surfaces leads to a significantly greater cost for consumable materials as well as additional down time for consumable replacement.
In an effort to eliminate the deficiencies of currently available systems, the present invention provides a plasma processing apparatus and method of controlling the etch chemistry within a plasma processing apparatus that achieves state-of-the-art oxide etch performance and meets the requirements for oxide etch processes without the need for using consumable materials.
The present invention advantageously provides a plasma processing apparatus including a processing chamber having an upper surface, a first gas inlet, and a second gas inlet. The plasma processing apparatus further includes a first wall extending from the upper surface into the processing chamber. The first wall encircles the first gas inlet, and the first wall has a base end and a terminal end, where the terminal end includes the second gas inlet. The plasma processing apparatus includes a first inductive coil provided within the first wall and encircling the first gas inlet, and a second inductive coil provided within the first wall and encircling the second gas inlet. Additionally, the plasma processing apparatus includes a first magnet array provided within the base end of the first wall adjacent the first gas inlet, and a second magnet array provided within the terminal end of the first wall adjacent the second gas inlet.
The present invention advantageously provides a plasma processing apparatus including a processing chamber having an upper surface, a first gas inlet, and a second gas inlet. The plasma processing apparatus includes a wall extending from the upper surface into the processing chamber. The wall encircles the first gas inlet, and the wall has a terminal end including the second gas inlet. The plasma processing apparatus includes a first injection region provided adjacent the first gas inlet, and a second injection region provided adjacent the second gas inlet. Additionally, the plasma processing apparatus includes means for providing a first magnetic field provided about the first injection region, and means for providing a second magnetic field provided about the second injection region.
The present invention advantageously provides a method of controlling plasma chemistry within a plasma processing apparatus. The method includes the steps of providing a first magnetic field about a first injection region in a processing chamber and providing a second magnetic field about a second injection region in the processing chamber. The method further includes the steps of introducing a first process gas into the first injection region via a first gas inlet, and introducing a second process gas into the second injection region via a second gas inlet. The processing chamber has a wall encircling the first gas inlet, such that the wall has a terminal end including the second gas inlet.